At Kyoto, we knew every final detail wouldn't be agreed at the negotiations. The important thing was to agree on principles – in Kyoto's case, on targets for emissions cuts – that could later be nailed down in a final legally binding agreement. But even though the deal agreed in Kyoto was a political one rather than a legal one, it still took until the 11th hour to strike an agreement between the three major players – the US, Japan and Europe.

The original proposal for a 5% reduction in greenhouse gases by 2012 (on 1990 levels) was quite rightly felt not to be sufficient. With the help of Al Gore, we managed to get the Japanese to go to 6%, provided it was less than the US. The US agreed to accept 7% as long as it was less than Europe, which we then set at 8% in order to secure an agreement.

That was the principle agreed on emissions cuts and later finalised during the next three years in what became known as the Kyoto protocol. The principle was to agree and later finalise at the following "conferences of the parties" (COPs – Copenhagen is number 15, hence COP15).

So the lesson I've learned from Kyoto for Copenhagen is that we were never going to be able to dot all the i's and cross the t's.

My recent discussions in the US with Obama's people and Congress members in September, talks in Europe with the Council of Europe, my meetings with China's environmental team as well as discussions in Abu Dhabi with ministers from the Arab oil producing countries last week, convince me all the more that my earlier judgment was right – that we will get an agreement in principle.

I also believe that the EU/China summit, which takes place in a fortnight, has the potential, especially after China's bilateral discussions with Obama, to help secure that agreement at Copenhagen.

Today, Hedegaard was speaking realistically about the need to prevent a breakdown at Copenhagen and emphasised the need for a framework for a roadmap that will, eventually, implement the principles of a binding agreement.

Now is a time for the art of the possible and that's the role of the negotiator – to achieve far more than the doomsayers predict, as we saw at Kyoto. At Kyoto when pressed by the journalists wanting an instant response on how the talks were going, I always said: "I'm walking and talking.''

So forget about doom and gloom. Let's all keeping walking and talking towards an agreement.

• John Prescott was an EU negotiator at Kyoto. He is the Council of Europe's climate change rapporteur and runs the New Earth Deal campaign.